1. Technical Field.
The invention relates generally to irrigation equipment and the like, and more particularly to a sprinkler featuring a new and improved externally adjustable valve.
2. Background Information.
Sprinklers sometimes include a manually operated valve for purposes of adjusting the flow rate. The valve is disposed within the sprinkler housing and operated by manipulation of an adjustment mechanism accessible from the housing exterior. With this arrangement, the valve can be conveniently adjusted after the sprinkler is installed to achieve a desired sprinkling flow rate.
The copending application identified above describes a new and improved pop-up sprinkler having an externally adjustable valve for this purpose. The valve element is driven with an externally-operated splined drive shaft to achieve more convenient, controlled valve adjustment while inhibiting undesired misadjustment. With the drive shaft construction, adjustment does not require manipulation of a wet stem, and the drive shaft and valve may employ gear reduction that makes fine adjustments more convenient and inadvertent misadjustment less likely.
However, there are certain aspects of the novel sprinkler described in that application that could be further improved. Consider certain details of its construction, for example. Generally, it includes a housing defining a hollow interior and an inlet port through which to supply a flow of liquid to the interior. A stem is disposed at least partially within the interior of the housing so that the stem can be moved between a retracted position and an extended position, and a piston disposed within the interior of the housing responds to the flow of liquid to move the stem.
The stem defines a passageway extending from a lower portion of the stem to a sprinkler head on an upper portion. The lower portion defines an opening through which the flow of liquid can pass from the interior of the housing into the passageway for passage to the sprinkler head, and a valve element moveably mounted on the stem at least partially blocks the opening. A shaft rotatably mounted on the housing extends to a position outside of the interior of the housing, and it is coupled to the valve element so that the valve can be rotated by rotation of the shaft for purposes of restricting the flow of liquid through the opening a selected amount.
More specifically, the illustrated valve element takes the form of a collar over a cylindrically-shaped portion of the stem so that the collar can be rotated relative to the stem to various alignments of an orifice in the collar and the opening in the stem. The valve element includes gear teeth which engage splines on the shaft for this purpose, and this provides gear reduction as well as maintaining coupling as the stem moves between the retracted and extended positions.
Although effective, this arrangement can be vulnerable to sand or other particulate material clogging or impairing movement of the valve element. The collar fits concentrically over the cylindrically-shaped portion of the stem, and this fit is somewhat close in order to inhibit water from leaking between the collar and stem. As a result, sand or other particulate material may become lodged between the collar and the stem and interfere with rotation of the valve element. In other words, the particulate material tends to cause the collar to bind or stick so that it may be somewhat difficult to rotate it by operation of the splined shaft.
Consequently, it is desired to have a new and improved pop-up sprinkler that alleviates this concern--one with a valve arrangement that is less vulnerable to becoming clogged by particulate material.